1. Field of the Invention
The present invention relates to an artificial joint such as an artificial knuckle joint, an artificial elbow joint and the like.
2. Description of the Prior Art
Conventionally, for example, a metacarpophalangeal joint of a finger (hereinafter, refer to an MP joint) is constituted by a metacarpal bone and a proximal phalanx, and a proximal interphalangeal joint (hereinafter, refer to a PIP joint) is constituted by a proximal phalanx and a phalanx media, however, when having an arthritis as typified by a rheumatoid arthritis, particularly joints, ligaments and tendons in hand and foot are gradually affected, so that a painful deformation, a significant limitation of motion or the like appears. As a countermeasure against the matter mentioned above, there has been generally executed an operation of replacing a joint portion deformed due to the arthritis by an artificial joint.
In this case, as the artificial joint mentioned above, there have been disclosed the following structures:
a. a structure in which stems are integrally formed in both ends of a middle flange portion around the middle flange portion with an elastic macromolecule material as typified by a silicon resin.
b. a spherical joint structure obtained by combining a spherical connection end with stems and a spherical surface recessed connection end with stems in a freely bending manner (refer to Japanese Utility Model Publication No. 2-29941 and Japanese Unexamined Patent Publication No. 9-38122).
c. a hinge joint structure obtained by pivoting a connection joint with stems each having an insertion hole by a pin in a freely bending manner (refer to Japanese Unexamined Patent Publication Nos. 59-91956 and 61-276553).
Accordingly, an operation to replace with the artificial joints mentioned above are done in accordance with a method of inserting a stem having a desired shape such as a rod shape, a tapered rod shape or the like into a bone marrow hole and fixing it via a bone cement, or a method of inserting a stem formed so as to fit to a required inner surface of the bone marrow hole into the bone marrow hole so as to fix.
However, the conventional artificial joint structured in the manner mentioned above can effectively achieve a joint function, but on the other hand, has a problem in a fixing method. For example, in the conventional method of inserting the stem formed in the tapered rod shape or the like into the bone marrow hole and fixing it via the bone cement, not only the fixing operation is very troublesome and needs a lot of work, but also there is a risk that a fixing force is easily weakened due to an aging of tissues within the bone marrow hole or the like, so that it is hard to hold the fixing force for a long time. Further, in the conventional method of inserting the stem formed so as to fit to the inner surface of the bone marrow hole into the bone marrow hole so as to fix, not only it is very troublesome to manufacture the stem so that a cost is increased, but also in the case that a shape suitability with respect to the tissues within the bone marrow hole lacks, there is a risk of a stress concentration which has conventionally been a great problem in view of a design.
An object of the present invention is to provide an artificial joint which can clear up the conventional problems mentioned above once for all, and can be rapidly, securely and easily fixed while being suited to an inner surface of a bone marrow hole by a novel structure absolutely different from the conventional one.
That is, in accordance with a first aspect of the present invention, there is provided an artificial joint comprising:
a stem base portion 10 in which a desired head 2 and a desired socket 5 are in slidably contact with each other in a freely bending manner, stems 9 and 16 are respectively attached fitly to free ends of the head 2 and the socket 5, and the respective stems 9 and 16 have therein locking screws 14 freely screwing to move along axial directions thereof; and
a pair of stem pieces 15 having an elasticity provided to protrude on both front portions of the stem base portion 10,
wherein the locking screws 14 are forcedly inserted within the stem pieces 15 so as to expand them outward, thereby making them tightly contact with and fix to inner surfaces of bone marrow holes 19 and 21.
Accordingly, the present invention described in the first aspect mentioned above is structured such as to expand the stem pieces 15 outward so as to tightly contact with and fix to inner peripheral surfaces of the bone marrow holes 19 and 21 while screwing the locking screws 14 so as to be forcedly inserted into the both side stem pieces 15, and fitly attach the head 2 and the socket 5 respectively to the stem base portion 10 so as to be in slidable contact in a freely bending manner.
In accordance with a second aspect of the present invention, there is provided an artificial joint as recited in the first aspect, wherein cuboid-shaped fitting pieces 3 and 7 are protruded from the free ends of the head 2 and the socket 5, quadrangular fitting holes 12 are formed in the stem base portions 10 in such a manner as to correspond to the fitting pieces 3 and 7, and the fitting pieces 3 and 7 are fitted and attached to the fitting holes 12.
Accordingly, since the invention described in the second aspect mentioned above is structured such as to fit and attach the cuboid-shaped fitting pieces 3 and 7 to the quadrangular fitting holes 12, not only it is possible to freely select positions for fixing within the bone marrow holes 19 and 21 while rotating the stems 9 and 16 at every 90 degrees, but also it is possible to adjust fixing positions of the head 2 and the socket 5 while adjusting fits thereof, thereby freely adjusting a tension of a collateral ligament.
In accordance with a third aspect of the present invention, there is provided an artificial joint as recited in the first aspect or the second aspect, wherein a constriction member mounting groove 4 is formed in one of the head 2 and the socket 5 so as to constrict a tendon sheath of flexor muscle 22, and constriction member mounting holes 8 are formed in the other of the head 2 and the socket 5 so as to constrict a tendon sheath of extensor muscle 23.
Accordingly, since the invention described in the third aspect is structured such that desired constriction members 17 are mounted to the constriction member mounting groove 4 and holes 8 so as to constrict the tendon sheath of flexor muscle 22 and the tendon sheath of extensor muscle 23 to the head 2 and the socket 5 by the constriction members 17, it is possible to securely prevent a movement to the ulna side.